1. Differential Pressure (ΔP) – Primary Quantified Standard
- Trigger: Current ΔP ≥ Initial ΔP + 500～600 Pa (at stable 330–350°C).
- Replace early if ΔP surges >300 Pa within 1 month – indicates pre-filter failure.
- Immediate replacement if ΔP suddenly drops – media tear or major leak.
2. PAO Integrity Scan Failure – GMP Mandatory
- Annual scan at ambient temperature.
- Replace if: Leak detected on media surface or ceramic adhesive layer that cannot be fixed by gasket replacement.
- Minor gasket seepage → replace gasket only.
- Media holes / adhesive cracks / separator deformation → replace entire filter.
3. Physical Damage – Visual Inspection
Replace on sight if:
- Media: scratches, holes, whitening, shedding
- Frame: distortion, pleat collapse
- Seal: adhesive peeling, powdering, through-cracks
- Irreversible caked dust / corrosion (rust/pitting)
4. Operational Anomalies
Replace if confirmed HEPA-related:
- Particle count exceeds ISO 5 limits (after excluding other causes)
- Endotoxin / particle batch failures traced to hot-air re-entrainment
- Persistent airflow decay with high blower load
- New leaks found in every semi-annual scan (thermal fatigue)
5. Time Reference – Backup Only (Not Standalone)
| Condition | Recommended Life |
|---|---|
| Standard (dual pre-filters, vertical mount) | 8–12 months |
| High-dust / high-breakage lines | 3–6 months |
| Lab ovens (low load) | Up to 14 months |
ΔP and PAO always override time.
Emergency Replacements (Immediate Shutdown)
- Overtemperature >380°C prolonged
- Physical puncture or compressed-air blow to media
- Oil/organic carbonization on media
- Incorrect horizontal or reverse installation
Quick Operator Checklist
| Frequency | Action |
|---|---|
| Weekly | Read ΔP; alert at +500 Pa |
| Annually | PAO scan – replace if unrepairable |
| Each inspection | Visual check of media, adhesive, frame |
| On data alarm | Investigate HEPA first |
| At max age | Preventive replacement |
Critical Reminders
- Never wait for full blockage – high ΔP tears media and ruins batches.
- Visual OK ≠ leak-free – micro-cracks are invisible; PAO is required.
- Never blow-clean – permanent efficiency loss.
- Adjust by load – clean lines may extend; dusty lines shorten life.
Post time: Jul-25-2026